Neural control system and method for alternatively fueled engines

ABSTRACT

A powertrain controller of a vehicle provides fuel injection pulses based on gasoline operation. The pulse widths of the fuel injection pulses are modified with reference to air temperature, engine speed, and exhaust gas oxygen (EGO) content to control fuel injectors for an alternative fuel such as natural gas. The EGO content, based on alternative fuel operation, is detected and compared to a desired air-fuel ratio or desired fuel trims to provide error information that is used to adjust the modification of the pulse widths. In response to the error information, a neural network (as an example) dynamically adjust the pulse widths of the alternative fuel injection based on the weights of measured, detected engine speed, EGO, universal exhaust gas oxygen, or air temperatures. The engine operating on alternative fuel is provided with the proper mixture of alternative fuel and air to respond to various engine loads and meet emission standards.

TECHNICAL FIELD

The present invention relates to a method and system for providingmultipoint gaseous fuel injection to an internal combustion engine foruse in various vehicles and engine-powered machines and moreparticularly, to a method and system for electrically controlling anengine operating on gasoline and alternative fuels.

BACKGROUND INFORMATION

Alternative fuels such as natural gas, hydrogen, propane, and ethanolare starting to enter the market in the transportation sector. This isdue to a number of factors, including lower price, reduced tailpipeemissions, and the security of the fuel supply in comparison to gasolineand diesel fuel. Furthermore, natural gas and propane reduce greenhousegas (GHG) emissions by about 25% compared to gasoline in automotiveapplications, while ethanol can reduce GHG emissions by about 30% to 65%depending on the process used to produce the ethanol. Similarly,hydrogen fuelled vehicles can reduce GHG emissions by about 60% to 80%.

Providing systems and methods to enable efficient and productive use ofalternative fuels is required.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention there is provideda method of modifying a fuel injection signal having a pulse width, thefuel injection signal being provided by a controller managing a fuelpowered apparatus receiving gasoline and an alternative fuel forelectrical control of a gasoline operated injector and analternative-fuel operated injector, the controller having information ontemperature, exhaust gas oxygen (EGO) content, air-fuel ratio, fueltrims and a control system type, the method comprising: (a) receivingthe pulse width of the fuel injection signal; (b) receiving theinformation on the temperature, the EGO content, and the fuel trims; (c)modifying the pulse width of the fuel injection signal based on thereceived information, the modified pulse width controlling alternativefuel supplied by the alternative fuel injector to the fuel poweredapparatus; (d) determining whether an error criterion is met based onmeasured information of the fuel powered apparatus operating on thealternative fuel and desired response information; and (e) repeating thesteps (c) and (d) when the error criterion is not met.

In accordance with another aspect of the present invention there isprovided a system for modifying a fuel injection signal having a pulsewidth, the fuel injection signal being provided by a controller managinga fuel powered apparatus receiving gasoline and an alternative fuel forelectrical control of a gasoline operated injector and analternative-fuel operated injector, the controller having information ontemperature, exhaust gas oxygen (EGO) content, air-fuel ratio, fueltrims and a control system type, the system comprising: a mechanismconstructed and adapted to obtain the pulse width of the fuel injectionsignal; a mechanism constructed and adapted to receive the informationon the temperature, EGO content and the fuel trims; a mechanismconstructed and adapted to modify the pulse width of the fuel injectionsignal based on the received information, the modified pulse widthcontrolling the alternative fuel supplied by the alternative fuelinjector to the fuel powered apparatus; and a mechanism constructed andadapted to determine whether an error criterion is met based on measuredinformation of the fuel powered apparatus operating on the alternativefuel and desired response information.

In accordance with another aspect of the present invention there isprovided a system for controlling fuel injection of an internalcombustion engine of a vehicle, the system comprising: sensors appliedto the vehicle for sensing parameters relating to the vehicle and thefuel injection; a controller for providing a fuel injection signalhaving a pulse width based on the sensed parameters; a fuel injector forinjecting a first fuel in a first mode and a second fuel in a secondmode into the engine; a comparator for comparing the sensed parameterswith reference parameters to provide an error signal; a pulse widthmodifier for changing the pulse width in response to the error signal;and a switch for providing the fuel injection signal to the fuelinjector and the pulse width modifier in the first and second modes,where: in the first mode, the fuel injector injects the first fuel intothe engine in response to the pulse width of the fuel injection signal,in the second mode, the fuel injector injects the second fuel into theengine in response to a modified pulse width of a modified fuelinjection signal, the modified pulse width being one changed by thepulse width modifier, the parameters sensed by the sensors in the secondmode being provided to the comparator, the comparator providing theerror signal in comparing the sensed parameters to the referenceparameters.

In accordance with another aspect of the present invention there isprovided a vehicle having an internal combustion engine comprising firstand second groups of fuel injectors, the first group of injectors beinggasoline injectors, the second group of injectors being alternative fuelinjectors; the vehicle comprising: sensing means for providinginformation on air for use in the engine, engine temperature, andexhaust gas oxygen content; control means for providing a fuel controlsignal having a pulse width in response to the information provided bythe sensing means; means for selecting a path of the fuel controlsignal; first fuel injection means for controlling the gasolineinjection by the gasoline injectors in response to the pulse width ofthe fuel control signal, while the path of the fuel control signal isselected to the first fuel injection means; pulse modification means formodifying the pulse width of the fuel control signal when the path ofthe fuel control signal is selected to the pulse modification means; andsecond fuel injection means for controlling the alternative fuelinjection by the alternative fuel injectors in response to a modifiedpulse width of the fuel control signal.

In accordance with another aspect of the present invention there isprovided a computer program product comprising a computer useable mediumhaving computer logic stored therein for modifying a fuel injectionsignal having a pulse width, the fuel injection signal being provided bya controller managing a fuel powered apparatus receiving gasoline and analternative fuel for electrical control of a gasoline operated injectorand an alternative-fuel operated injector, the controller havinginformation on temperature, exhaust gas oxygen (EGO) content, air-fuelratio, fuel trims and a control system type, the computer programproduct including: a mechanism constructed and adapted to obtain thepulse width of the fuel injection signal; a mechanism constructed andadapted to receive the information on the temperature, EGO content andthe fuel trims; a mechanism constructed and adapted to modify the pulsewidth of the fuel injection signal based on the received information,the modified pulse width controlling the alternative fuel supplied bythe alternative fuel injector to the fuel powered apparatus; and amechanism constructed and adapted to determine whether an errorcriterion is met based on measured information of the fuel poweredapparatus operating on the alternative fuel and desired responseinformation.

In accordance with another aspect of the present invention there isprovided a computer-readable media tangibly embodying a program ofinstructions executable by a computer to perform a method of modifying afuel injection signal having a pulse width, the fuel injection signalbeing provided by a controller managing a fuel powered apparatusreceiving gasoline and an alternative fuel for electrical control of agasoline operated injector and an alternative-fuel operated injector,the controller having information on temperature, exhaust gas oxygen(EGO) content, air-fuel ratio and fuel trims, the method comprising: (a)receiving the pulse width of the fuel injection signal; (b) receivingthe information on the temperature, EGO content, and the fuel trims; (c)modifying the pulse width of the fuel injection signal based on thereceived information, the modified pulse width controlling thealternative fuel supplied by the alternative fuel injector to the fuelpowered apparatus; (d) determining whether an error criterion is metbased on measured information of the fuel powered apparatus operating onthe alternative fuel and desired response information; and (e) repeatingthe steps (c) and (d) when the error criterion is not met.

In accordance with another aspect of the present invention there isprovided, in a vehicle controller, in which a fuel injection signalhaving a pulse width is modified, the fuel injection signal beingprovided by the vehicle controller managing a fuel powered apparatusreceiving gasoline and an alternative fuel for electrical control of agasoline operated injector and an alternative-fuel operated injector,the controller having information on temperature, exhaust gas oxygen(EGO) content, air-fuel ratio and fuel trims, a memory medium comprisingsoftware programmed to provide the modified fuel injection signal by amethod comprising: (a) receiving the pulse width of the fuel injectionsignal; (b) receiving the information on the temperature, EGO content,and the fuel trims; (c) modifying the pulse width of the fuel injectionsignal based on the received information, the modified pulse widthcontrolling the alternative fuel supplied by the alternative fuelinjector to the fuel powered apparatus; (d) determining whether an errorcriterion is met based on measured information of the fuel poweredapparatus operating on the alternative fuel and desired responseinformation; and (e) repeating the steps (c) and (d) when the errorcriterion is not met.

In an exemplary embodiment, the step of modifying the pulse width can beperformed by a separate microprocessor from the powertrain controller.The separate microprocessor receives various signals from the engine andoutputs the pulse width for the alternative fuel. In some cases themicroprocessor affects control over the powertrain controller bymodifying the gasoline pulse width for the alternative fuel whilepreventing the fuel trims on the powertrain controller from saturating.In other cases the powertrain controller affects control over themicroprocessor by utilizing the fuel trims from the powertain controllerto control the pulse width.

For example, the alternative fuel is natural gas and thus, the engineoperates on gasoline and/or natural gas. In the method for modifying afuel injection signal, as the measured information, a value of an EGOcontent while the engine is operating on the alternative fuel. Also, asthe desired response information, a desired air-fuel ratio as thedesired response information is provided. In response to the measuredinformation and the desired response, the pulse width of the fuelinjection signal provided by the powertrain controller is modified. Theengine operating on alternative fuel is provided with the proper mixtureof the alternative fuel and air to respond to various engine loads andmeet emission standards.

For example, the alternative fuel is natural gas and thus, the engineoperates in a bi-fuel manner, that is, gasoline or natural gas. In thesystem for modifying a fuel injection signal, a value of an EGO whilethe engine is operating on the alternative fuel is obtained and adesired air-fuel ratio is provided. In response to the value of the EGOand the desired air-fuel ratio, the pulse width of the fuel injectionsignal provided by the powertrain controller is modified. The engineoperating on the alternative fuel is provided with the proper mixture ofthe alternative fuel and air to respond to various engine loads and meetemission standards.

For example, the alternative fuel is natural gas and thus, the engineoperates in a bi-fuel manner, that is, gasoline or natural gas. Thesystem modifies the pulse width of the fuel injection signal provided bythe powertrain controller, in response to a value of an EGO or fuel trimsignals while the engine is operating on the alternative fuel at thedesired air-fuel ratio. Therefore, the engine operating on thealternative fuel is provided with the proper mixture of the alternativefuel and air.

For example, the alternative fuel is natural gas and thus, the engineoperates in a bi-fuel manner, that is, gasoline or natural gas. Thepulse modification means modifies the pulse width of the fuel controlsignal, in response to a value of an EGO while the engine is operatingon the alternative fuel and the desired air-fuel ratio. In response tothe modified pulse width, the second fuel injection means controls thealternative fuel injection of the second group of injectors. Therefore,the engine operating on the alternative fuel is provided with the propermixture of the alternative fuel and air and the vehicle is operated onvarious engine load conditions and meets emission standards.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram showing a control system for a bi-fuelengine and a neural control system (NCS) according to an embodiment ofthe present invention;

FIG. 2 illustrates an implementation functional block diagram of theNCS;

FIG. 3 is a functional diagram showing a detail of the NCS;

FIG. 4 is a flowchart showing the overall operation of the NCS;

FIG. 5 is a block diagram showing a detailed configuration of the NCSutilizing a universal exhaust gas oxygen (UEGO) sensor output fortraining when a powertrain control module (PCM) is in an open-loop or aclosed-loop;

FIG. 6 shows NCS outputs (lambda, closed-loop gain and pulse width) tothe UEGO in the closed-loop status of the PCM in training at idle at acoolant temperature Thw of 90° C.;

FIG. 7 shows NCS outputs (fuel trims, lambda and closed-loop gain) tothe UEGO in the closed-loop status of the PCM in training at idle at acoolant temperature Thw of 90° C.;

FIG. 8 shows NCS output responses (lambda and pulse with) to theacceleration from the idle conditions at a coolant temperature Thw of90° C.;

FIG. 9 shows NCS outputs (lambda, open-loop gain and pulse width) withthe UEGO in the open-loop status of the PCM in training at idle at acoolant temperature Thw of −10° C.;

FIG. 10 is a block diagram showing a detailed configuration of the NCSutilizing an EGO sensor output for training when the PCM is in anopen-loop or a closed-loop condition;

FIG. 11 shows NCS outputs (lambda, closed-loop gain and pulse width)with the EGO at the closed-loop status of the PCM in training at idle ata coolant temperature Thw of 90° C.;

FIG. 12 shows NCS output responses (fuel trims, weight, lambda andclose-loop gain) to the EGO in the closed-loop status of the PCM intraining at idle at a coolant temperature Thw of 90° C.

FIG. 13 shows NCS outputs (lambda, open-loop gain and pulse width) inthe open-loop status of the PCM in training at idle at a coolanttemperature Thw of −10° C.;

FIG. 14 is a block diagram showing a detailed configuration of the NCSutilizing short-term and long-term fuel trims (STFT, LTFT) for trainingwhen the PCM is in a closed-loop;

FIG. 15 illustrates NCS output responses (fuel trims, lambda andclosed-loop gain) to training utilizing the STFT and LTFT in theclosed-loop status of the PCM if PWcl<1.15 PWol at a coolant temperatureThw of 90° C.;

FIG. 16 illustrates NCS output responses (fuel trims, lambda andopen-loop gain) to training utilizing the STFT and LTFT in theclosed-loop status of the PCM if PWcl >1.15 PWol at a coolanttemperature Thw of 90° C.;

FIG. 17 illustrates a three-layered neural network used in neuralcontrol system;

FIG. 18 is a block diagram showing a detailed configuration of the NCSutilizing a UEGO sensor output for training with two neural controllers;

FIG. 19 illustrates a neural controller;

FIG. 20 illustrates the structure of the neuron;

FIG. 21 illustrates training process; and

FIG. 22 is a block diagram showing a detailed configuration of the NCSutilizing fuel trim control.

DETAILED DESCRIPTION

I. Technical Background

Engines in vehicles must be supplied with the proper mixture of fuel andair to respond to various engine loads and meet tailpipe emissionstandards. This is the responsibility of the engine fuel controlcomputer commonly called a powertrain control module (PCM). A PCMincludes a microprocessor and associated memory chips, input/outputdevices and the like, and is programmed by a vehicle manufacturer tocontrol engine functions such as air and fuel intake. The PCM receivesdata concerning engine operation from many electrical andelectromechanical sensors. Within each PCM, there are certain operatingparameters, or coefficients, for which values are preset based oncharacteristics of the fuel used and engine displacement. Theseparameters are called calibration coefficients, and their values affectfuel consumption, performance of the engine, and emissions produced.

In gasoline fuel-injected engines, the PCM is calibrated based ongasoline properties. Gasoline is stored as a liquid and must bevaporized for combustion over a −40° C. to +40° C. ambient temperaturerange. Hence, engine calibration is not a trivial matter and consists ofa host of algorithms and tables containing calibration coefficients.Most engines utilize a speed-density correlation to calculate therequired fuel flow rate given the airflow rate through the engine. Theairflow rate is either measured directly or calculated from themeasurement of the engine speed (Ne), intake air density, enginedisplacement, and volumetric efficiency. The fuel flow rate iscalculated from the desired (i.e., stoichiometric) air-fuel ratio andair flow rate. In stoichiometric combustion there is enough oxygen toconvert all the fuel into completely oxidized products.

The required fuel injector pulse width is then calculated from the fuelflow rate based on an equation for flow rate of the injector that isused in the engine. If the speed-density pulse width is used to activatethe injector without air-fuel ratio feed back, the operation is termedopen-loop control. For closed-loop control aproportional-integral-derivative (PID) controller with oxygen sensorfeedback is usually used to control air-fuel ratio at nearstoichiometric conditions to optimize the efficiency of the catalyst inthe exhaust gas stream, minmizing tailpipe emissions.

The output of the PID controller, which is called the short-term fueltrim (STFT), modifies the speed-density pulse width to correspond tofeed back from the oxygen sensor. Long-term fuel trim (LTFT) is used toadjust the pulse width for disturbances like clogged air filters orclogged injectors while maintaining a stoichiometric air-fuel ratiocontrol. Usually the LTFT is calculated from the STFT in such a way thatas the LTFT increases as the STFT decreases, preventing the STFT fromsaturating. However, if the STFT or LTFT compensate the speed-densitypulse width by more than 35%, for example, they become saturated. Thiswill generate a problem/trouble code on an on-board diagnosis (OBD)system, which will cause the control system to go to open-loop controland register an engine trouble code, illuminating a “check-engine”light.

When alternative fuels are to be used in an engine designed forgasoline, the PCM must be re-calibrated for the new fuel. In the case ofusing gaseous fuels like natural gas, propane, or hydrogen thedifference in calibration values can be substantial, and the cost ofre-calibration can be expensive given the large number of engines.

The following additional equipment is typically required to adapt agasoline fuel-injected engine to natural gas, hydrogen, or propane: agas storage tank, a gas regulator, gas fuel injectors, and a computercalibrated for the alternative fuel. When this equipment is installed inparallel with the gasoline fuel system, the vehicle can be either run onthe alternative fuel or on gasoline at the flick of a switch, which istermed bi-fuel. If access to the calibration tables is not provided bythe PCM's original equipment manufacturer (OEM), then a separate controlcomputer is installed in parallel with the PCM. Such a fuel controlsystem is known and includes all the auxiliary equipment mentionedabove, plus sensors that measure a manifold air pressure MAP, an intakeair temperature Tha, an engine speed Ne, and a coolant temperature Thw.The separate control computer contains calibration tables as well ascontrol algorithms/software mentioned above for the alternative fuel.

Modern gasoline engine fuel control systems utilize pulse-widthmodulation to control the amount of fuel entering an engine. Forexample, a fuel injector can be activated for 7 (ms) at every sparkevent (or ignition) to provide fuel at the engine idle condition. Whenan alternative fuel system like natural gas is used, the values for theinjector pulse width must be changed to say 6 (ms) for natural gasinjection, a factor of 0.86 decrease in pulse width. If this doesn'thappen, the engine will run rich of stoichiometry, resulting in reducedpower output, higher exhaust emissions, engine codes being set, andpossible engine damage.

A fuel control system may also include control signals, generated by thePCM. The control signals are modified by a factor taken from analternative fuel control module, and are used to activate an independentfuel control valve to supply an alternative fuel to the engine. Whilesuch systems can be sufficient when the vehicle is fully warmed up andoperating at a certain operating point, they are unacceptable duringengine start, warm-up, acceleration, and deceleration. An additionalproblem is that different calibration factors are required for eachengine on the market. If a single factor is used, the engine will notstart in cold weather; acceleration will be poor; and tailpipe emissionswill increase significantly.

For example, during engine start at −20° C. the pulse width on gasolinemust be reduced from 110 (ms) to 18 (ms) on natural gas to start theengine, a decrease by a factor of 6 in pulse width. However, at idle thepulse width must be decreased by a factor of 0.75 at −20° C. This issufficiently different than the factor of 0.86 decrease for a fully warmengine mentioned above that can cause drivability problems and enginetrouble codes. The problem is that one factor is insufficient to produceacceptable performance and emissions over the fullspeed-load-temperature range of an engine. Nor will one factor work forall the engines on the market. A complete range of factors, or set ofcalibration tables, is required for different engines operating underdifferent loading and environmental conditions. Providing these tablesis costly given the time required for manual calibration.

Methods for calculating the factors (mentioned above) between thegasoline and natural gas pulse width based on the temperature of the gasand the energy content of the two fuels are known in the art. Thesetypes of conventional systems improve operation to a certain extent;however, it is too simplistic to cover the full speed-load-temperaturerange of an engine. This is particularly true during significantgasoline enrichment at cold-start, acceleration, or power enrichmentphases of operation.

The present invention describes a system and a method for determining arange of factors suitable for a particular engine that are establishedwhile the engine is running on the road. Various control techniques havebeen developed that will train gasoline engines to operate on naturalgas, propane, hydrogen, or ethanol producing acceptable performance,driveability and emissions over the full operating range.

A host of factors can be installed in a calibration table that canoperate the engine over the full speed-load-temperature range; however,this requires considerable time to be spent on a dynamometer calibratingthe engine. The control system and method of the present inventionpresents a technique for the engine to calibrate itself for analternative fuel as the vehicle is driven on a chassis dynamometer or onthe road, reducing calibration costs.

By way of background, the various techniques of the present inventioncan use (in exemplary embodiments) neural network control. A neuralnetwork is a massively parallel distributed processor made up of simpleprocessing units, which has a natural propensity for storingexperiential knowledge and masking it for available use. Neural networkshave learning and adaptation capabilities, thus neural networks can workas a “black box” without requiring a priori knowledge of the plantdynamics under control.

Neural networks are also adaptive systems, but do not require a model ofthe system. They “learn” or create an internal structure that reflectsthe system dynamics (linear or nonlinear) through continuous or batchtraining. Their performance relies on the richness and the informationcontent of the signals that are used for their training.

II. Background of the Present Invention

In exemplary embodiments, the present invention presents an intelligentcontrol system that utilizes neural network techniques to self-calibratean auxiliary computer, or microprocessor, for natural gas, hydrogen,propane, or ethanol as a fuel.

By way of background, for example, the present invention provides aneural network to adapt gasoline engines to operate on alternativefuels. The method is based on a number of separate arrays of neuronsthat are trained by separate algorithms when the PCM is under closedloop or open loop control. The training algorithms modify the gasolinepulse width produced by the PCM, a pulse width calculated separately,for natural gas, hydrogen, propane, or ethanol combustion.

In a first example, training is conducted utilizing a universal exhaustgas oxygen (UEGO) sensor or a wide range oxygen sensor that measures theair-fuel ratio as a linear function of oxygen content of the exhaust. Ina second example, training is conducted by conventional exhaust gasoxygen (EGO) sensors or a “bang—bang” oxygen sensor that indicates ifthe exhaust is rich or lean of stoichiometry as a function of the oxygenconcentration of the exhaust. The output of the sensor is 1 volt if theexhaust is rich or zero volt if the exhaust is lean. In control systemsvocabulary this non-linear sensor is termed a “bang—bang” oxygen sensor,which indicates if a switch is on or off in other applications. A thirdexample utilizes the short-term fuel trim (STFT) and long-term fuel trim(LTFT) from the PCM for training when the PCM is in the closed-loopcondition.

III. Embodiments

FIG. 1 shows a control system for an engine operating on gasoline and analternative fuel according to an embodiment of the present invention. Inthe embodiment, the alternative fuel is natural gas. It may be anothergaseous fuel, for example, propane. The system includes a bi-fuelalternative fuel system 110. Air taken through a filter 112 enters aninternal combustion engine 114 through an intake 116 and it passesthrough a throttle 118 to an intake manifold 120. Within the alternativefuel system 110, with a bi-fuel switch 122 in its natural gas position“a”, fuel from a natural gas fuel tank 124 passes through a shut-offsolenoid valve 126, a regulator 128, and alternative fuel or natural gasfuel injectors 132 and is mixed with air in the intake manifold 120. Thealternative fuel system 110 includes a computer, or microprocessor,containing a neural control system (NCS) 130 for modifying the pulsewidths of a signal from a powertrain control module (PCM) 140.

The engine 114 is a multi-port, fuel-injected engine. Most multi-port,fuel-injected engines can have up to eight natural gas injectors, onefor each cylinder. The eight natural gas injectors are additional toeight gasoline injectors for bi-fuel applications. For throttle-bodyfuel injection systems, there is usually one or two injectors located upstream of the throttle. The present invention can be applied to bothmulti-port and throttle-body fuel-injection systems and with engineshaving ten or more cylinders.

The PCM 140, which can be provided by an original equipmentmanufacturer, generates a gasoline injection signal Sinj having aninjection pulse width PWoem. The signal Sinj is a series of triggeredsynchronized pulses which change between 0 V and 12 V, where 0 V is thecondition for the injector to be open and 12 V is the condition for theinjector to be closed. The pulse width PWoem is measured by the NCScomputer 130 where it is modified to a pulse width PWn for natural gascombustion according to neural control algorithms (discussed in detailbelow).

The NCS computer 130 provides a natural gas injection signal Salt havingthe modified injection pulse width PWn. The signal Salt is fed to thenatural gas fuel injectors 132 through injector drivers (not shown) toactuate them. The resultant fuel flow rates from the natural gas fuelinjectors 132 control the composition of the air-fuel mixture that isdrawn into the engine 114. With the bi-fuel switch 122 in a gasolineposition “b”, the gasoline injection signal Sinj having the injectionpulse width PWoem is fed directly to the gasoline injectors 142 throughinjector drivers (not shown) and thus, the alternative fuel controlsystem 110 is by-passed. Gasoline from a gasoline tank (not shown) isfed to the gasoline injectors 142 and is mixed with air in the intakemanifold 120.

Various sensors provide the PCM 140 with their sensing outputs or sensedvalues. An air temperature sensor 162 provides an intake air temperatureTha. An engine speed sensor 164 provides an engine speed Ne. A coolanttemperature sensor 166 provides a coolant temperature Thw. A throttleposition sensor 168 provides a throttle position Poth. An exhaust gasoxygen (EGO) sensor 170 provides an indication if the engine is runningrich or lean of stoichiometry. A universal exhaust gas oxygen (UEGO)sensor 172 provides a UEGO or an indication of lambda, the actualair-fuel ratio. The EGO sensor and/or the UEGO sensor are used tocontrol the air-fuel ratio of the exhaust near stoichiomentric tooptimize the efficiency of a catalyst 190. The catalyst 190 improvestailpipe emissions by removing carbon monoxide, oxides of nitrogen, andhydrocarbons from the exhaust. A manifold air pressure (MAP) sensor 174provides a MAP value. A mass airflow (MAF) sensor 176 provides a MAFvalue. An exhaust gas recirculation (EGR) sensor 178 provides an EGRvalue.

In some engines, a UEGO sensor 172 replaces the EGO sensor 170. Engineload is determined by either the MAP or MAF, depending on the engine.The EGR sensor 178 is included in the engine 114 to reduce tailpipeemissions of oxides of nitrogen.

The MAF, Tha, Poth and MAP sensors 176, 162, 168 and 174 have respectivesensing devices 177, 163, 169 and 175, which are positioned in the airintake stream. The Ne sensor 164 has sensing devices 165 that arelocated in the engine 114. The Thw, EGO and UEGO sensors 166, 170 and172 have respective sensing devices 167, 171 and 173, which arepositioned in the gaseous exhaust stream. The sensing outputs (MAF, Tha,Poth, MAP, Ne, EGR, Thw, EGO and UEGO) are used by the PCM 140 tocontrol the air-fuel mixture by generating the injection pulse widthPWoem. This maintains consistent operation of the engine 114 undervarious operating conditions on gasoline. The PCM 140 is generallyinstalled in a vehicle (not shown) at the time of manufacture to runusing gasoline as fuel.

The alternative fuel system 110 is provided with the NCS computer 130,which is an auxiliary computer or a microprocessor inserted between thePCM 140 and the natural gas fuel injectors 132. The NCS computer 130measures the injection pulse width PWoem received from the PCM 140 andconverts it into the output pulse width PWn that can be used to operatethe natural gas fuel injectors 132. The pulse width PWoem generated bythe PCM 140 is based on the fuel being gasoline. The NCS computer 130drives and controls the natural gas fuel injectors 132 when alternativefuel is used in the alternative fuel system 110 and allows a properair-fuel mixture to be maintained when an alternative fuel such asnatural gas is used in the engine 114. The NCS computer 130 alsoreceives sensing outputs Tha, MAF, MAP, Ne, EGR, Thw, Tha, EGO and UEGOfrom the respective sensors.

Furthermore, the NCS computer 130 receives information on on-boarddiagnostics (OBD), including: the open-loop status (ol) or theclosed-loop status (cl) of the PCM 140, signals of the short-term fueltrim (STFT) and the long-term fuel trim (LTFT) from an OBD system 182 onthe PCM 140. The OBD system 182 continuously monitors a plurality ofoperating parameters (e.g., over 50) on the vehicle as the vehicle isrunning to determine if they are in the proper range. If they are out ofrange, a code will be recorded internally identifying the problem. Thiscode can be retrieved at a service center with the proper monitoringequipment for the vehicle. If the code is persistent and will not clearin normal use, then the engine malfunction indicator or check enginelight on the dashboard of the vehicle is illuminated.

FIG. 2 shows a functional block diagram of the alternative fuel system110 with the NCS. The NCS computer 130 included in the alternative fuelsystem 110 has a parameter (or weight) determination system 210. Thedetermination system 210 calculates values for the operating weights ofthe alternative fuel system 110 according to the type of fuel being usedand characteristics of the engine 114. The operating weights will varyaccording to different types of fuel that may be used and the size andtype of engine. The determination system 210 includes a feed forwardneural control (FFNC) module 222 that receives the gasoline injectionsignal Sinj having the pulse width PWoem from the PCM 140, varioussensor outputs (MAP, Thw, Tha) and the fuel trims (STFT and LTFT) fromthe OBD system 182.

Within the NCS computer 130, an array of weights are continuouslyadjusted by a training algorithm in a neural feed back training module(NFBT) module 224 based on an error between a desired air-fuel ratioRref and a measured air-fuel ratio Rmeas. A subtraction circuit 228 isprovided with the desired air-fuel ratio Rref by a reference settingdevice 226. Also, the subtraction circuit 228 is provided with EGO orUEGO, as the measured air-fuel ratio Rmeas. The training error can alsobe based on the long-term fuel trim (LTFT) from the OBD system 182. Thesubtraction circuit 228 provides an error (Rref−Rmeas) to the NFBTmodule 224 which in turn calculates the training weights for the FFNCmodule 222.

The MAP from the MAP sensor 174, the Thw from the Thw sensor 166 and theTha from the Tha sensor 162 are also provided to the NFBT module 224.

In the NCS computer 130 (of the present embodiment), the trainingcontinues until an error criteria is satisfied, and then training isstopped. During the training, the weight determination system 210calculates operating weights. In the present embodiment, the NCScomputer 130 is capable of being used and adapts to a large number ofdifferent fuels. The NCS computer 130 has two functions: (1) adjustingor modifying the fuel injection pulse width based on the neural weightsin the FFNC module 222, and (2) measuring air-fuel ratio in the exhauststream (EGO or UEGO), or the fuel trims (LTFT or STFT) from the OBDsystem 182 on the PCM 140, for the NFBT module 224 for use incalculating the training weights.

In the training mode, the FFNC module 222 uses the values of the sensoroutputs and the fuel trims to determine proper operating parametervalues (weights) for the fuel being used. The NFBT module 224 is usedwhen there are air-fuel ratio (i.e., EGO or UEGO) changes or the fueltrim (i.e., STFT or LTFT). These changes may be due to installation ofthe NCS computer 130 in a different vehicle with a different enginedisplacement, the use of a different fuel, or some other changes thataffect the operation of the alternative fuel system 110.

The sensor outputs and the fuel trims are fed to the FFNC module 222where operating parameter values are applied to the values of the sensoroutputs and the fuel trims and processed according to a controlalgorithm. A result from the processing is used to create a controlsignal for the natural gas fuel injectors 132. In the NFBT module 224,the result is combined with the desired air-fuel ratio Rref to determinehow closely the weights in the FFNC module 222 are to proper values forthe system (i.e., values that produce the ideal response). The result ofthe combination of the desired ratio Rref and the response from the FFNCmodule 222 is processed by the NFBT module 224 that adjusts theoperating parameter values, or training weights, so that the outputresponse from the FFNC module 222 to the sensor outputs will be as closeas possible to the desired ratio Rref In this case, the desired ratioRref is near the stoichiometric air-fuel ratio control to optimizeexhaust emissions and maintain the fuel trims on the PCM belowsaturation.

Once the weights are adjusted and training is completed, the next stepis to test the FFNC module 222 response to inputs it has not seenbefore. This can be done on the road or on a dynamometer. If the FFNCmodule 222 responds correctly with good driveability, acceptable power,and acceptable tailpipe emissions, it is said that generalization of theneural network has taken place, no further training will be necessary,and the vehicle is deemed road worthy.

FIG. 3 shows a functional block diagram of the NCS computer 130 thatincludes a master computer module 310 (e.g., an 8, 16, or 32-bit (orlarger) microprocessor) and first and second slave computer modules 312and 313. The slave computer modules 312 and 313 are connected to themaster computer module 310 through buffers 314 and 315, respectively.The two slave computer modules 312 and 313 measure the pulse width of upto four gasoline fuel injectors 142 each through a conditioning circuit316 and an opto-isolation module 318.

The two slave computer modules 312 and 313 also calculate the correctnatural gas mixture using pulse width PWn for up to four natural gasfuel injectors 132 for each slave module. The eight neural pulse widthsPWn are passed through opto-isolation circuitry 320 and eight injectordrivers 322 to activate each natural gas fuel injector 132 in its propersequence for combustion in each cylinder.

The weight determination system 210 shown in FIG. 2 is located in themaster computer module 310. This is where the training algorithm in theNFBT module 224 updates the array of neurons in the FFNC module 222shown in FIG. 2. The master computer module 310 also reads thecrankshaft position or some other sensors to determine the engine speedNe from the sensor 164. In addition, it reads the following engineoperating parameters MAP or MAF, EGO or UEGO, Thw, Tha, a fuel type TYfu(from a fuel type sensor (not shown)) and a battery voltage Vbat (from avoltage sensor (not shown)). The signals of these parameters or valuesare provided to the master computer module 310 through a connectorcircuit 328 and respective circuits: i.e., an opto-isolation circuit332, amplifiers 334, 336, 338, buffers 340, 342, 346, and opto-couplers344, 348. Also, the master computer module 310 receives through asuitable interface 354 information on whether the air-fuel ratiocontroller in the PCM 140 is in the open-loop status (ol) or in theclosed-loop status (cl) and on the fuel trims, STFT and LTFT.

FIG. 4 is a flow chart showing the operation of a neural type process ofthe NCS computer 130 shown in FIG. 1. The neural process is initiatedwith an ignition switch (not shown) in its “on” position (step 401), andthe bi-fuel switch 122 shown in FIG. 1 (e.g., a dashboard mounted fuelswitch) in its natural gas (or alternative fuel) position “a”. Thisopens the natural gas shut-off solenoid valve 126 (step 402), runs asetup program (step 403), and initiates self-diagnostics (step 404). Theneural program then enters its main loop at A 405. The first action isto read the following engine sensor outputs at step 406 (the Ne sensor164, the MAP sensor 174 or MAF sensor 176, the EGO sensor 170 or theUEGO sensor 172, the Thw sensor 166, the Tha sensor 162, the fuel typesensor, and the battery voltage sensor).

The signals from the OBD system 182 on the PCM 140 shown in FIG. 1 arethen read via the interface 354 shown in FIG. 3. This determines if thecontrol system in the PCM 140 is in the open-loop status (ol) or theclosed-loop status (cl) on the line 356 shown in FIG. 3, and reads theSTFT value on the line 358 and the LTFT value on the line 360. There canbe two STFTs and two LTFTs in engines with more than four cylinders,such as one for each side of a V6 or V8 engine. As well, all sensorsignals described above are not always required.

In the next step, the two slave computer modules 312 and 313 read pulsewidths PWoem generated by the PCM 140. In a case of the pulse widthsrelating to the gasoline injectors 142 at cylinders 1, 3, 5 and 7 in aneight-cylinder engine (true at step 407), the first slave computermodule 312 reads the pulse widths (step 409). In a case of the pulsewidths being relating to the gasoline injectors 142 at cylinder 2, 4, 6and 8 in the eight-cylinder engine (true at step 408), the second slavecomputer module 313 reads the pulse widths (step 409).

In the next step, the period between injections is calculated (step410). This is followed in sequence by the following operations orcalculations for open- and closed-loop operation of the PCM 140:

At step 411, neural controller weights, Wcl, Wol, and Wolcl are read.

At step 412, neural controller outputs, GAINcl and GAINol arecalculated. GAINcl is a closed-loop gain and GAINol is an open-loopgains.

At step 413, neural controller pulse widths, PWsd, PWol and PWcl arecalculated. PWsd is a theoretical pulse width or a standard speeddensity natural gas pulse width. PWcl is a closed-loop pulse width or amodified gasoline pulse width from the PCM 140. PWol is an open-looppulse width or a modified standard speed density natural gas pulsewidth.

PWol is based in part on the calculation of a theoretical pulse widthPWsd from a speed-density relationship and in part on GAINol. At step414, it is determined if the PCM 140 is in the closed-loop status (cl)and if the PWcl is less than PWol by a certain factor (in this case thefactor is 1.3). This factor can in practice range between 1 and 1.5. Ifthis is true at step 414, then the output pulse PWn will be set equal toPWcl (step 415). If not, the PWn will be set equal to PWol (step 416).

The next part of the control process involves training the weights Wol,Wcl, and Wolcl for open- and closed-loop operation. It is determined atstep 417 if the engine speed Ne is greater than 600 rpm, if the EGOsensor 170 or the UEGO sensor 172 is active and if the error criterionis not met between the desired Rref and the measured air-fuel ratio, orlong-term fuel trim, Rmeas (see FIG. 2).

When the step 417 determination is true, the neural controller weightfor closed-loop, Wcl, is trained (step 418). Following step 418 and whenthe step 417 determination is false, the program returns to point A 405and the cycle repeats itself. Following step 416, it is determinedwhether open-loop training is required (step 419). Wol is trained (step420) if the engine speed (Ne) is greater than 600 rpm and if the exhaustgas oxygen sensor (EGO or UEGO) is active and if the error criterion isnot met between the desired Rref and the measured air-fuel ratio Rmeas.

The training weight Wolcl covers a condition where the PCM is closedloop, but PWcl >1.3 PWol. Wolcl is trained (step 420) if the enginespeed (Ne) is greater than 600 rpm and if the exhaust gas oxygen sensor(EGO or UEGO) is active and if the error criterion is not met betweenthe desired Rref and the measured LTFT Rmeas. The control loop thencycles back to point A 405, and the sensor outputs are read again (step406). When the ignition system is turned off (true at step 421), theprocess is complete.

EXAMPLE

FIG. 5 shows an example of a neural control system (NCS) according to anexemplary embodiment of the present invention using the UEGO fortraining and the OBD port to determine whether the PCM 140 is in theclosed-loop status (cl) or the open-loop status (ol).

The EGO sensor 170 provides a bang—bang (EGO) signal to the PCM 140. Asmentioned earlier, the first and second slave computer modules 312, 313shown in FIG. 3 measure the pulse width PWoem_(t) at each gasolineinjector actuator event at time t. In the first example of the NCS shownin FIG. 5, a single slave computer 510 (corresponding to the slavecomputer 312 or 313 in FIG. 3) and a master computer (corresponding tothe master computer module 310 shown in FIG. 3) for measuring the pulsewidth and performing the training are shown. The second slave is notshown for clarity.

A closed-loop training switch 511 is provided that is selected if thePCM is closed loop (at its position “cl₂”), an open-loop training switch513 for selecting the open-loop status (at its position “ol₂”) and apulse width calculator 530 including a speed-density algorithm for thetheoretical pulse width PWsd at time t. Switch 511 at position cl₂activates closed-loop training in element 550; at position cl₁, cl=0 andtraining is stopped. Switch 513 at position ol₂ activates open-looptraining in element 560; at position ol₁, ol=0 and training is stopped.

FIG. 5 shows two main loops for calculating a neural pulse width at timet, PWn_(t), which operate the alternative fuel or natural gas fuelinjectors 132: one for calculating the closed-loop pulse width at timet, PWcl_(t), and another for calculating the open-loop pulse width attime t, PWol_(t). Which pulse width is used depends on whether the PCM140 is in the closed-loop status (cl) or the open-loop status (ol) andwhether PWcl_(t) is some factor (e.g., 30%) greater than PWol_(t). Theprocess proceeds as follows: initially, PWn_(t)=PWol_(t); however, ifthe PCM 140 is in the closed-loop status cl and PWcl_(t)<1.3 PWol_(t),then PWn_(t)=PWcl_(t).

PWcl_(t) is calculated using the following relationships at time t, thetime that the PWoem_(t) event takes place:

PWcl _(t) =GAINcl _(t) PWoem _(t-2)  (1)

The output of the closed-loop neural controller, GAINcl_(t), iscalculated from the training weight, Wcl_(t) (i, j, k), as follows:

GAINcl _(t)=1+Wcl _(t)(i, j, k)  (2)

Wcl_(t) (i, j, k) is a thee-dimensional array of weights with thefollowing coordinates: i=coolant temperature (Thw); j=manifold airpressure (MAP) or manifold air flow (MAF); k=engine speed (Ne).

PWol_(t) is calculated from the following relationships at time t:

PWol _(t)=GAINol_(t) PWsd_(t)  (3)

GAINol _(t)=1+Wol _(t)(i, j, k)  (4)

The following training algorithms are used to calculate the twothree-dimensional arrays that store the closed-loop weights, Wcl (i, j,k), and open-loop weights, Wol (i, j, k):

Wcl _(t)(i, j, k)=Wcl _(t-1)(i, j, k)+μPeriod_(t) SIG _(t)  (5)

Wol _(t)(i, j, k)=Wol _(t-1)(i, j, k)+μPeriod_(t) SIG _(t)   (6)

where μ=training rate.

The time or sampling interval between injections, Period_(t), iscalculated from the following equation: $\begin{matrix}{{Period}_{t} = \frac{60 \cdot 1000 \cdot 2}{{NeN}_{cyl}}} & (7)\end{matrix}$

where

Ne=engine speed (rpm), and

N_(Cyl)=number of cylinders in the engine.

In automotive engineering, the air-fuel ratio A/F is defined by theratio of the air mass flow rate ma and the fuel mass flow rate m_(f).

In stoichiometric combustion, there is enough oxygen to convert all thefuel into completely oxidized products. The air-fuel ratio at whichcomplete combustion takes place is called the stoichiometric air-fuelratio A/F_(s) and lambda (λ) is defined as the ratio of A/F and A/F_(s).The error SIG_(t) between the desired ratio Rref defined by thestoichiometric condition (λ_(s)=1) and the actual air-fuel ratio Rmeasmeasured by the UEGO sensor (λ) is determined from the followingequation:

SIG _(t)=1−λ  (8)

Training the open and closed-loop weights, Wol_(t) (i, j, k) and Wcl_(t)(i, j, k), proceeds as follows: Initially, both the open-loop andclosed-loop training switches shown in FIG. 5 are not in the trainingmode (ol=ol₁ and cl=cl₁). Open-loop training can be continuous becausesaturating the STFT value or the LTFT value in the PCM 140 is notpossible. However, if this is troublesome, an error criteria can beapplied as follows: If the absolute error, SIG_(t) is greater than 0.05(5%) or less than 0.4 (40%), then ol=ol₂ and open-loop training begins.In the closed-loop mode if the absolute error, SIG_(t), is greater than0.05 or less than 0.4, then cl=cl₂ and closed-loop training begins.

Air flowrate, m_(a), through the engine can be measured utilizing theMAF sensor 176, or calculated using a speed-density algorithm in thepulse width calculator 530. A theoretical base pulse width PWsd_(t)based on the airflow rate m_(a) and fuel flow rate m_(f), can becalculated as follows: $\begin{matrix}{m_{a} = {\eta_{v}\rho \quad V\frac{Ne}{2}}} & (9) \\{m_{f} = \frac{m_{a}}{A/F_{s}}} & (10)\end{matrix}$

where

η_(v)=the volumetric efficiency of the engine

ρ=inlet air density

V=volumetric displacement of the engine

The mass of fuel injected into a cylinder can be calculated as follows:$\begin{matrix}{M_{f} = \frac{2\quad m_{f}}{{NeN}_{cyl}}} & (11)\end{matrix}$

Substituting equation 9 into 10 and equation 10 into 11 yields thefollowing: $\begin{matrix}{M_{f} = \frac{\eta_{v}\rho \quad V}{{A/F_{s}}N_{cyl}}} & (12)\end{matrix}$

A formula for the required pulse width, PWsd, in (ms) for a fuelinjector can be expressed by the following linear equation:

PWsd=k _(f) M _(f) +T _(v)  (13)

where

k_(f)=injector coefficient

T_(v)=injector off set (ms)

Substituting equation 12 into 13 provides the speed-density pulse widthas follows: $\begin{matrix}{{PWsd}_{t} = {\frac{k_{f}\eta_{v}\rho \quad V}{{A/F_{s}}N_{cyl}} + T_{v}}} & (14)\end{matrix}$

The volumetric efficiency can be estimated from the followingtheoretical relationship: $\begin{matrix}{\eta_{v} = {\left( \frac{M}{M_{a}} \right)\left( \frac{MAP}{P_{a}} \right)\left( \frac{T_{a}}{T_{ha}} \right)\frac{1}{\left\lbrack {1 + \left( {F/A} \right)} \right\rbrack}\left\{ {\frac{r_{c}}{r_{c} - 1} - {\frac{1}{\gamma \left( {r_{c} - 1} \right)}\left\lbrack {\left( \frac{P_{e}}{MAP} \right) + \left( {\gamma - 1} \right)} \right\rbrack}} \right\}}} & (15)\end{matrix}$

where

M=molecular weight of the mixture

M_(a)=molecular weight of air

MAP=manifold air pressure

P_(a)=atmospheric pressure

Tha=intake air temperature

Ta=atmospheric air temperature

F/A=fuel-air ratio=1/A/F

r_(c)=engine compression ratio

P_(e)=exhaust pressure

γ=ratio of specific heat at constant pressure and specific heat atconstant volume

Alternatively, PWsdt can be estimated by the following empiricalrelationship:

PWsd _(t) =aMAP+b Ne+c  (16)

where coefficients a, b, and c are determined experimentally.

A computer model of the NCS and internal combustion engine has beendeveloped to evaluate and test the NCS shown in FIG. 5. The objective isfor the NCS to adjust lambda (λ) to the desired response (λ_(s)=1) whilepreventing the STFT and LTFT values from saturating. Model predictionsare shown in FIGS. 6 and 7 where each curve is designated by numerals 1to 5 with legends provided in the drawing. At engine idle (Ne=800 rpm,MAP=250 mmHg, Poth=12°) when the PCM 140 is in the closed-loop status(cl) at a coolant temperature Thw of 90° C. As shown in FIG. 6, the NCSoutput, GAINcl, reduces from 1 to 0.86. This reduces PWn from an initialvalue of 7.1 (ms) to 5.9 (ms) over a period of 5 (s), as shown in FIG.6. During the same period, lambda (λ) increases from 0.8 to 1.0, and thePCM 140 creates a limit cycle in lambda (λ) at the 6 (s) mark whichoptimizes the catalyst efficiency, reducing tailpipe emissions. Theresults shown in FIG. 7 indicate that the training weight, Wcl,decreases from 0 to −0.14, and that the STFT starts to toggle at anaverage value of −0.077 at 6 (s). It then increases to an average valueof 0, while the LTFT moves from 0 to −0.09. Hence, the STFT and the LTFTdo not saturate, which would occur at values of ±0.35 in many vehicles.As mentioned earlier, saturation can cause engine trouble codes andcheck-engine lights.

FIG. 8 shows the pulse width response to acceleration from the idleconditions, mentioned earlier, to cruise (engine speed=2000 rpm, MAP=400mmHg, Poth=300) in 0.5 (s). A spike occurs in PWoem (curve 3) due togasoline acceleration enrichment strategies on the PCM, peaking at 23(ms). However, since the NCS limits PWn to 1.3 PWol, this reduces thepulse width PWn to 13 (ms), and consequently a spike in lambda (curve 1)is reduced to an acceptable value of 0.85 between the 75 and 75.5 (s).

In many vehicles at coolant temperatures Thw below 0° C., the PCM isopen-loop. Training the NCS at −10° C. under the same idle conditionsmentioned earlier is shown in FIG. 9. Under these circumstances PWol isinitially set to PWsd=6.7 (ms). The NCS controller output, GAINol,decreases from 1 to 0.92, reducing PWol from 6.7 (ms) to 6.2 (ms).Concurrently, lambda increases from 0.8 to 0.95 when training is stoppedbecause the 0.05 (5%) error criteria in met. Both the STFT and LTFT arezero because the PCM 140 is in the open-loop status. They are onlyapplied in the closed-loop operation.

EXAMPLE

FIG. 10 shows an example of a NCS according to an exemplary embodimentof the present invention. This example is similar to the above example,except that the sensor EGO 170 (for a bang—bang signal) is used to trainthe neural network instead of the UEGO sensor 172 (linear signal).Similar to training with the UEGO sensor 172, open-loop training can becontinuous, but closed-loop training cannot be continuous because thefuel trims will saturate if the bang—bang signal is even slightlyunbalanced.

However, if continuous training is troublesome, open-loop andclosed-loop training can be terminated in two ways:

(i) In a first example of termination, training will be terminated ifthe EGO, once it is active, changes its status from rich (+1:>0.5 volt)to lean (−1:<0.5 volt) or vise versus. At this point the new errorsignal is not equal to the error signal at the previous time increment(SIG_(t)≠SIG_(t-1)). Similar to the first example for open-looptraining, the engine speed Ne must be greater than 600 rpm for trainingto take place and the EGO must be active. Regarding the closed-looptraining, training will take place if the PCM 140 is in the closed-loopstatus cl and if the engine speed Ne is greater than 600 rpm and ifSIG_(t) is equal to SIG_(t-1).

(ii) In a second example of termination, training will be terminated ifthe frequency, f, of the air-fuel ratio limit cycle is less than thetheorectical frequency, f_(th), of the limit cycle expressed by thefollowing equation: $\begin{matrix}{f_{th} = \frac{1}{4\quad T}} & (17)\end{matrix}$

where

T=the transport delay between the fuel injectors and the EGO sensor 170.

FIG. 11 shows the NCS output, GAINcl, at idle and Thw=90° C. while thePCM 140 is in the closed-loop status cl. Similar to training with theUEGO, GAINcl decreases from 1.0 to 0.89, reducing PWn initially from 7.2(ms) to 5.9 (ms) over a 10 (s) period. At the same time, lambda (λ)increases from 0.8 to about 1.0 where it starts to oscillate in a limitcycle between 0.98 and 1.02 after the 10 (s) mark. At this point,training is stopped because SIG_(T)≠SIG_(t-1). As shown in FIG. 12, theSTFT initially decreases to an average value of −0.11 at 10 (s), thenincreases to oscillate (toggle) about zero at 72 (s). Concurrently, Woldecreases to −0.11 as well at 10 (s), and the LTFT decreases from 0 to−0.12 after 72 (s). Since LTFT is less than ±0.35, saturation does notoccur, and the engine will perform acceptably well without illuminatinga check engine light.

Training with the EGO at idle at a coolant temperature of −10° C. andwhen the PCM is in the open-loop status (ol) and EGO is active is shownin FIG. 13. Similar to training with the UEGO, the NCS controlleroutput, GAINol, decreases from 1.0 to 0.87, reducing PWol initially from6.7 (ms) to 5.9 (ms) at 10 (s). Concurrently, lambda (λ) increases from0.8 to 1.01, as which point training is stopped.

EXAMPLE

FIG. 14 shows an example of the NCS according to an exemplary embodimentof the present invention. In the third example, the LTFT is used totrain the NCS when the PCM 140 is in the closed-loop status (cl)(instead of training utilizing the UEGO or the EGO as in the first andsecond examples), as follows:

PWcl_(t) is calculated from the following relationships at time t, thetime that the PWoem_(t) event takes place (similar to Equation 1):

PWcl _(t) =GAINcl _(t) PWoem _(t−2)  (18)

The output of the closed-loop neural controller, GAINcl_(t), iscalculated from the training weight, Wcl_(t−1)(i, j, k), as follows:

GAINcl _(t)=1+Wcl _(t)(i, j, k)+STFT  (19)

Wcl_(t−)(i, j, k) is a thee-dimensional array of weights with thefollowing coordinates: i=coolant temperature (Thw); j=manifold airpressure (MAP) or manifold air flow (MAF); k=engine speed (Ne).

PWol_(t) is calculated from the following relationships at time t:

PWOl _(t) =GAINol _(t) PWsd _(t)  (20)

If the PCM is closed loop, but PWcl>1.15 PWol:

GAINol _(t)=1+Wol _(t)(i, j, k)+Wolcl _(t)(i, j, k)+STFT+LTFT  (21)

For this example the factor between PWcl and PWol has been reduced from1.3 to 1.15 to improve response.

The training processes are similar to those used in the previousexamples (Equations 7 and 8); however, the closed-loop desired responseRref is LTFT=0. Hence, the training error, SIGLT_(t)=0+LTFT. However,Wolcl_(t)(i, j, k) is calculated as follows:

Wolcl _(t)(i, j, k)=Wolcl_(t−1)(i, j, k)+μPeriod _(t) SIG _(t)  (22)

Training Wolcl will take place if the PCM 140 is in the closed-loopstatus (cl) and if the engine speed Ne is greater than 600 rpm and ifthe absolute value of SIGLT_(t) is greater than 0.05 or less than 0.4.The STFT signal from the PCM 140 is used to improve response.

Switch 515 is used to stop training if cl and PWcl>1.15 PWol as follows:

lt=lt₂

If cl and PWcl<1.15 PWol then lt=lt₁=0

In the present example, a fuel trim section switch 541 is included forselecting the STFT to avoid changes in enrichment (spikes) duringtransients that in some cases are included in STFT. Switch 541 is open(st=st₁=0) during significant transients in PWoem or rpm; however, ifthere is only small change in PWoem or rpm switch 541 closes (st=st₂) asfollows for the sampling interval of Δ{acute over (ω)} and ΔPWoem:

st=st₁=0

If −3<Δ{acute over (ω)}<3 then st=st₂

If −4<ΔPWoem<4 then st=st₂

where {acute over (ω)}=injection frequency=1/Period

Δ{acute over (ω)}=the change frequency during the sampling interval, and

ΔPWoem=the change in pulse width during the sampling interval.

In the present example, the open-loop training can be conducted in thesame manner as in either of the previous examples. FIG. 14 shows thatthe EGO sensor 170 is used for continuous open-loop training as in thesecond example if the EGO is active.

FIG. 15 shows the model predictions for Wcl training at cruise (enginespeed=2000 rpm, MAP=400 in Hg, Poth=30°) and a coolant temperature Thwof 90° C. utilizing the STFT for fast response and the LTFT forclosed-loop training. Unlike the previous examples, the initialcondition is a lean air-fuel ratio of lambda λ=1.3 (instead of rich).The NCS output, GAINcl, initially increases from 1 to 1.12 over 13 (s)in the first step due largely to the STFT feed back, then increases from1.12 to 1.22 at 85 (s) in the second step due to LTFT training. Wclincreases from zero at 20 (s) to 0.23 at 75 (s). If a significant changein engine speed (rpm) or pulse width (PWoem) occurs then STFT isdisconnected at switch 541.

In the first step, the LTFT increases to 0.17, then in the second stepit reduces to 0.04 until training is stopped at 75 (s). The examplespresented earlier limit the LTFT to some value; however, the presentexample is unique because it reduces the LTFT to near zero (0.04), adefinite improvement. Concurrently, the STFT feed back to the NCSreduces lambda (λ) from 1.3 to toggling about 1 in about 12 (s).Subsequently, the combination of the LTFT and Wcl reduce the STFT to alimit cycle about zero.

FIG. 16 shows the model predictions for Wolcl training at cruise (enginespeed=2000 rpm, MAP=400 in Hg, Poth=30°) and a coolant temperature Thwof 90° C. STFT is used for fast response and the LTFT for closed-looptraining. For this case PWcl>1.15 PWol; hence PWn=PWol, although the PCMis closed loop. The initial condition is a lean air-fuel ratio of lambdaλ=1.23. The NCS output, GAINol, increases from 1 to 1.23 over 13 (s)largely due to the STFT feed back. Wolcl increases from zero at 0 (s) to0.12 at 12 (s). If a significant change in engine speed (rpm) or pulsewidth (PWoem) occurs, then STFT is disconnected at switch 541.

In the first step, LTFT increases to 0.08, then in the second step itreduces to 0.04 until training is stopped at 45 (s). Similar to above,LTFT is reduced to near zero (0.04), a definite improvement.Concurrently, the STFT feed back to the NCS reduces lambda (λ) from 1.23to toggling, or limit cycle, about 1 in about 12 (s). Subsequently, thecombination of the LTFT and Wolcl reduce the STFT to a limit cycle ofideally about zero (i.e., the desired condition).

EXAMPLE

FIG. 17 illustrates an example of a three layered neural network withtan-sigmoid activation functions according to an exemplary embodiment ofthe present invention. Four and eight neurons are respectively used inthe first and the second layers. The output layer has one neuron. Basedon sensitivity studies with various inputs, two inputs are selected asinputs to the neural network. The inputs sent to the neural network areengine speed, Ne, oxygen sensor output, UEGO, speed density functionpulse width, PWsd, and output of the neural networks with a unit delay,which makes the network dynamic.

The learning algorithm used to train the neural network iscomputationally efficient and is known as the Alopex algorithm. TheAlopex learning algorithm adapts the neural network weights directlybased on the output error E, of the system and does not use atransformed version of the error, which is normally done in other neuralnetwork based control schemes.

E=y _(d)(t)−y(t)  (23)

where yd and y are the desired and the actual output.

Each weight, w, in the network is changed based on a probability index Pof going in the right direction, so that the global error function isminimized. During an t^(th) iteration in time, the weight change isgiven as,

w(t)=w(t−1)+δ(t)  (24)

where δ(t) is a small positive or negative step of size δ with thefollowing probabilities:

δ(t)=−δ with probability P(t)

=+δ with probability [1−P(t)]

The probability is given by:

P(t)=1/(1+exp[−Δ(t)/T)])  (25)

where Δw(t)=w(t−1)−w(t−2) and ΔE(t)=E(t−1)−E(t−2) are the changes inweight and error measure over the previous two iterations and Δ(n) is acorrelation measure A between the change in weight and change in systemerror and Δ(n) is given by:

Δ(t)=Δw(t)ΔE(t)  (26)

The algorithm takes biased random walks in the direction of decreasingerror, measured over the previous two iterations. The weights of thenetwork are initialized at small random values and are updated at eachtime step (incremental updating). The temperature T is a positivetemperature that determines the effective randomness in the system.Initially, T is set to a large value and subsequently, is set equal tothe average value of the correlation calculated at every 50 iterations.This method automatically reduces the temperature T when parameters areclose to optima where the correlations are small.

EXAMPLE

FIG. 18 shows an example of the NCS according to an exemplary embodimentof the present invention. In the present example, two controllers areused: a first multi-layered neural controller 1 (MNC1) 550 and a secondmulti-layered neural controller 2 (MNC2) 560 that are used when the PCM140 is in the closed-loop and open-loop, respectively. The training forthe controllers is on-line and is continuously performed. The objectivefor the MNC1 550 in closed-loop operation is to modify the gasolinepulse width, PWoem, adjusting lambda (λ) to the desired value (λ=1),while preventing the short-term (STFT) and long-term (LTFT) fromsaturating on the PCM. The objective for the MNC2 560 in open-loopoperation is to modify the pulse width from the pulse with calculator530 having a speed-density process/algorithm to ensure the relativeair/fuel ratio is near stoichiometric while PCM 140 is in open-loop. TheMAP and UEGO values sensed by the MAP sensor 174 and the UEGO sensor 172are used for control, which can be described in detail as follows:

(i) In a case of the PCM 140 being in the closed-loop and PWcl<1.3PWsd:

PWn_(t)=PWcl_(t)  (27)

PWcl _(t) =PWoem _(t) ×GAINcl _(t)  (28)

GAINcl _(t)=1+Wcl _(t)  (29)

Wcl_(t)=Ψ[.]  (30)

where

PWn=natural gas pulse width (ms)

PWcl=modified gasoline pulse width (ms) from the PCM 140

PWoem=gasoline pulse width (ms) from the PCM 140

GAINcl=closed-loop gain

Wcl=output of neural controller 550

Ψ[.]=nonlinear activation of neural controller

(ii) In a case of the PCM 140 being in the open-loop:

PWn_(t)=PWol_(t)  (31)

Pwol _(t) =PWsd _(t) ×GAINol _(t)  (32)

GAINol _(t)=1+Wol _(t)  (33)

PWsd _(t) =aMAP+bNe+c  (34)

PWsd can also be calculated utilizing Equation 16.

where

PWol=modified standard speed density natural gas pulse width (ms)

PWsd=standard speed density natural gas pulse width (ms)

MAP=manifold air pressure (mm Hg)

Ne=engine speed (rpm)

a,b,c=three coefficients which are determined experimentally

GAINol=open-loop gain

Wol=output of neural controller 560

(iii) In a case of the PCM 140 being in the closed-loop andPWcl>1.3PWsd:

PWn_(t)=PWol_(t)  (36)

Two training algorithms will be explained after showing the structure ofneural network controller: i) modified back propagation, and 2) modifiedAlopex.

A neural-network-based controller can be considered as a general classof adaptive controller. The basic feature of a neural controller is theability to learn and adapt. The structure of the neural controller usedin the present example is a three-layered neural network with onefeedback connection within the network as shown in FIG. 19. Eachcomputing element in the network is called a neuron, and itsmathematical model is shown in FIG. 20.

The basic training (learning) process for a neural controller isdemonstrated in FIG. 21 (similar to FIG. 2), where x(t) is the inputsignal, u(t) is the output signal from the controller, y(t) and yd(t)are the actual and desired system output. The error signal is definedas:

e(t)=y _(d)(t)−y(t)  (37)

The error signal is used to adapt the neuron weights (WT) so as tominimize the performance index J(t) which is defined as:

J(t)=E{F[e(t,WT)]}

A commonly used form of F[.] is a squared function of error, then$\begin{matrix}{{J(t)} = {{\frac{1}{2}E\left\{ {^{2}(t)} \right\}} = {\frac{1}{2}\frac{1}{N}{\sum\limits_{m = {t - N + 1}}^{t}\left\lbrack {^{2}(m)} \right\rbrack}}}} & (38)\end{matrix}$

Where N is the number that indicates the amount of past information usedin the calculation of J(t).

The updated (adaptation) equations for the adjustable neural weights aredefined as:

WT _(1j)(t+1)=WT _(1j)(t)+ΔWT _(1j)(t)  (39)

There are different training processes/algorithms associated with theupdating of neural weights.

Two processes are discussed: modified error back propagation (backwardsubstitution) (MBP) and modified Alopex (MAL).

(i) Modified Back Propagation

The back propagation algorithm is a gradient decedent method thatminimizes the error between the desired outputs and the actual outputsof the networks, and the error is back propagated layer by layer andused to update the weights of the networks. The derivation of MBPalgorithm is based on the back propagation method. Using the steepdecent approach, the adjustments in the weights are given by:$\begin{matrix}{{\Delta \quad {{WT}_{ij}(t)}} = {{- \mu}\frac{\partial{J(t)}}{\partial{WT}_{ij}}}} & (40)\end{matrix}$

Where μ is the learning rate which determines the rate of convergence ofthe learning algorithm.

Equation (40) can be written in detail, as follows: $\begin{matrix}\begin{matrix}{{\Delta \quad {{WT}_{ij}(t)}} = {{- \mu}{\frac{\partial}{\partial{WT}_{ij}}\left\lbrack {\frac{1}{2}\frac{1}{N}{\sum\limits_{m = {t - N + 1}}^{t}{^{2}(m)}}} \right\rbrack}}} \\{= {{- \mu}\frac{1}{N}\quad {\sum\limits_{m = {t - N + 1}}^{t}{{e(m)}\left\lbrack {\frac{\partial\quad}{\partial{WT}_{ij}}{e(m)}} \right\rbrack}}}} \\{= {{- \mu}\frac{1}{N}\quad {\sum\limits_{m = {t - N + 1}}^{t}{{e(m)}{\frac{\partial\quad}{\partial{{WT}_{ij}(m)}}\left\lbrack {{y_{d}(t)} - {y(t)}} \right\rbrack}}}}} \\{= {\mu \frac{1}{N}\quad {\sum\limits_{m = {t - N + 1}}^{t}{{e(m)}\frac{\partial\quad}{\partial{{WT}_{ij}(m)}}{y(t)}}}}} \\{= {\mu \frac{1}{N}\quad {\sum\limits_{m = {t - N + 1}}^{t}{{e(m)}\frac{\partial{y(t)}}{\partial{u(t)}}\frac{\partial{u(t)}}{\partial{{WT}_{ij}(t)}}}}}}\end{matrix} & (41)\end{matrix}$

up to now, a basic MBP algorithm is provided.

(ii) Modified Alopex

Refer to the Alopex algorithm discussed earlier, Equation (24) can berewritten as:

WT _(1j)(t+1)=WT _(1j)(t)+δ(t)  (42)

and

δ(t)=+δ when ΔWT increase and ΔE decrease, or ΔWT decrease and ΔEincrease

δ(t)=+δ when ΔWT decrease and ΔE deccrease, or ΔWT increase and ΔEincrease where δ is small positive size.

A schematic of another learning strategy that uses fuel trim (STFT andLTFT) to train the neural controller when the PCM 140 is closed-loop isshown in FIG. 22. This is a case of NCS control with STFT and LTFT at aninjection pressure Pj=125 psig and a coolant temperature Thw=90° C. Thestructure is similar to the structure in FIG. 14. The training algorithmis to make the closed-loop desired response LTFT be close to zero. TheLTFT decreases with the increasing of learning iteration. The finalvalue of LTFT is within the rage of −0.05 to +0.05.

Although particular embodiments of the present invention have beendescribed in detail, there are numerous variations. It should beappreciated that numerous variations, modifications, and adaptations maybe made without departing from the scope of the present invention asdefined in the claims.

What is claimed is:
 1. A method of modifying a fuel injection signalhaving a pulse width, the fuel injection signal being provided by acontroller managing a fuel powered apparatus receiving gasoline and analternative fuel for electrical control of a gasoline operated injectorand an alternative-fuel operated injector, the controller havinginformation on temperature, exhaust gas oxygen (EGO) content, air-fuelratio, fuel trims and a control system type, the method comprising: (a)receiving the pulse width of the fuel injection signal; (b) receivingthe information on the temperature, the EGO content, and the fuel trims;(c) modifying the pulse width of the fuel injection signal based on thereceived information, the modified pulse width controlling alternativefuel supplied by the alternative fuel injector to the fuel poweredapparatus; (d) determining whether an error criterion is met based onmeasured information of the fuel powered apparatus operating on thealternative fuel and desired response information; and (e) repeating thesteps (c) and (d) when the error criterion is not met.
 2. The method ofclaim 1, further including (a) providing the alternative fuel to thealternative fuel injector, the alternative fuel injector beingconfigured to operate on the alternative fuel, the alternative fuelbeing one of: natural gas, propane, and hydrogen; and (b) providing thegasoline to the gasoline injector.
 3. The method of claim 1, whereinstep (d) includes: obtaining a value of the EGO content as the measuredinformation; and providing a desired EGO content as the desired responseinformation.
 4. The method of claim 1, wherein step (d) includes:obtaining a value of the air-fuel ratio as the measured information; andproviding a desired air-fuel ratio as the desired response information.5. The method of claim 1, wherein step (c) includes: determining aclosed-loop pulse width in response to the pulse width of the fuelinjection signal when the control system type is closed-loop, theclosed-loop pulse width, the alternative fuel supplied by thealternative fuel injector and the determination of the error criterionbeing performed in response to the closed-loop pulse width.
 6. Themethod of claim 5, further comprising adjusting the closed-loop pulsewidth based on speed density information of the fuel powered apparatus.7. The method of claim 1, wherein step (c) includes: determining anopen-loop pulse width in response to the pulse width of the fuelinjection signal when the control system type is open-loop, theopen-loop pulse width, the alternative fuel supplied by the alternativefuel injector and the determination of the error criterion beingperformed in response to the open-loop pulse width.
 8. The method ofclaim 7, further comprising adjusting the open-loop pulse width based onspeed density information of the fuel powered apparatus.
 9. The methodof claim 1, wherein step (d) includes: obtaining the fuel trimsinformation as the measured information; and providing desired fueltrims information as the desired response information.
 10. The method ofclaim 9, wherein the step of obtaining the fuel trims informationincludes obtaining a measured short-term fuel trim.
 11. The method ofclaim 9, wherein the step of obtaining the fuel trims informationincludes obtaining a measured long-term fuel trim.
 12. The method ofclaim 9, wherein the step of obtaining the fuel trims informationincludes obtaining a measured short-term fuel trim and a measuredlong-term fuel trim.
 13. The method of claim 12, wherein step (d)includes: obtaining a value of the air-fuel ratio as the measuredinformation; and providing a desired air-fuel ratio as the desiredresponse information.
 14. The method of claim 13, wherein step (c)includes: determining a closed-loop pulse width in response to the pulsewidth of the fuel injection signal when the control system isclosed-loop, the closed-loop pulse width and the determination of theerror criterion being performed in response to the closed-loop pulsewidth.
 15. The method of claim 14, further comprising adjusting theclosed-loop pulse width based on speed density information of the fuelpowered apparatus.
 16. The method of claim 15, further comprisingobtaining information on temperature of the fuel powered apparatus inoperation.
 17. The method of claim 16, further comprising obtaining thespeed density information of the fuel powered apparatus.
 18. The methodof claim 17, wherein step (c) includes changing the pulse width inresponse to the temperature information, the speed density informationand the value of the air-fuel ratio.
 19. A system for modifying a fuelinjection signal having a pulse width, the fuel injection signal beingprovided by a controller managing a fuel powered apparatus receivinggasoline and an alternative fuel for electrical control of a gasolineoperated injector and an alternative-fuel operated injector, thecontroller having information on temperature, exhaust gas oxygen (EGO)content, air-fuel ratio, fuel trims and a control system type, thesystem comprising: a mechanism constructed and adapted to obtain thepulse width of the fuel injection signal; a mechanism constructed andadapted to receive the information on the temperature, EGO content andthe fuel trims; a mechanism constructed and adapted to modify the pulsewidth of the fuel injection signal based on the received information,the modified pulse width controlling the alternative fuel supplied bythe alternative fuel injector to the fuel powered apparatus; and amechanism constructed and adapted to determine whether an errorcriterion is met based on measured information of the fuel poweredapparatus operating on the alternative fuel and desired responseinformation.
 20. The system of claim 19, wherein the mechanism todetermine includes: a mechanism constructed and adapted to obtain avalue of the EGO content as the measured information and to provide adesired EGO content as the desired response information.
 21. The systemof claim 19, wherein the mechanism to determine includes: a mechanismconstructed and adapted to obtain a value of the air-fuel ratio as themeasured information and to provide a desired air-fuel ratio as thedesired response information.
 22. The system of claim 19, wherein themechanism to determine includes: a mechanism constructed and adapted toobtain the fuel trims information as the measured information and toprovide desired fuel trims information as the desired responseinformation.
 23. The system of claim 19, wherein the mechanism to modifythe pulse width includes: a mechanism constructed and adapted todetermine a closed-loop pulse width in response to the pulse width ofthe fuel injection signal when the control system type is closed-loop,the closed-loop pulse width, the alternative fuel supplied by thealternative fuel injector and the determination of the error criterionbeing performed in response to the closed-loop pulse width.
 24. Thesystem of claim 23, wherein the mechanism to determine the closed-looppulse width includes a mechanism constructed and adapted to adjust theclosed-loop pulse width based on speed density information of the fuelpowered apparatus.
 25. The system of claim 19, wherein the mechanism tomodify the pulse width includes: a mechanism constructed and adapted todetermine an open-loop pulse width in response to the pulse width of thefuel injection signal when the control system type is open-loop, theopen-loop pulse width, the alternative fuel supplied by the alternativefuel injector and the determination of the error criterion beingperformed in response to the open-loop pulse width.
 26. The system ofclaim 25, wherein the mechanism to determine the open-loop pulse widthincludes a mechanism constructed and adapted to adjust the open-looppulse width based on speed density information of the fuel poweredapparatus.
 27. A system for controlling fuel injection of an internalcombustion engine of a vehicle, the system comprising: sensors appliedto the vehicle for sensing parameters relating to the vehicle and thefuel injection; a controller for providing a fuel injection signalhaving a pulse width based on the sensed parameters; a fuel injector forinjecting a first fuel in a first mode and a second fuel in a secondmode into the engine; a comparator for comparing the sensed parameterswith reference parameters to provide an error signal; a pulse widthmodifier for changing the pulse width in response to the error signal;and a switch for providing the fuel injection signal to the fuelinjector and the pulse width modifier in the first and second modes,where: (i) in the first mode, the fuel injector injects the first fuelinto the engine in response to the pulse width of the fuel injectionsignal, (ii) in the second mode, the fuel injector injects the secondfuel into the engine in response to a modified pulse width of a modifiedfuel injection signal, the modified pulse width being one changed by thepulse width modifier, the parameters sensed by the sensors in the secondmode being provided to the comparator, the comparator providing theerror signal in comparing the sensed parameters to the referenceparameters.
 28. The system of claim 27, wherein the first fuel includesgasoline and the second fuel includes an alternative fuel, the firstmode being a gasoline operation mode, the second mode being analternative fuel operation mode.
 29. The system of claim 28, wherein thefuel injector comprises first and second injectors, the first injectorinjecting the gasoline into the engine in the first mode and the secondinjector injecting the alternative fuel into the engine in the secondmode.
 30. The system of claim 28, wherein the controller includes meansfor determining the fuel injection signal in response to the sensedparameters in the first mode, the fuel injection signal having agasoline pulse width for enabling operation of the engine on thegasoline.
 31. The system of claim 30, wherein the controller includesmeans for determining the fuel injection signal in response to thesensed parameters in the second mode, the fuel injection signal havingan alternative fuel pulse width for enabling operation of the engine onthe alternative fuel.
 32. The system of claim 31, wherein the pulsewidth modifier includes means for changing the gasoline pulse width ofthe fuel injection signal to the modified pulse width in response toparameters sensed during operation of engine on the alternative fuel.33. The system of claim 32, wherein the alternative fuel includes agaseous fuel.
 34. The system of claim 33, wherein the gaseous fuel isone of propane and hydrogen.
 35. The system of claim 33, wherein thegaseous fuel includes natural gas, the second mode being a natural gasoperating mode, the fuel injector including first and second injectorsfor injecting the gasoline and the natural gas.
 36. The system of claim35, wherein the sensors include an exhaust gas oxygen (EGO) sensor forobtaining an EGO content and an engine temperature sensor for obtainingan engine temperature, wherein the sensed parameters are formulated fromthe EGO content and the engine temperature.
 37. The system of claim 36,wherein the controller includes means for providing information on aclosed-loop status of the controller.
 38. The system of claim 37,wherein the pulse width modifier includes means for varying the pulsewidth in response to the EGO content, the engine temperature and theclosed-loop status.
 39. The system of claim 35, wherein the sensorsinclude a universal exhaust gas oxygen (UEGO) sensor for obtainingair-fuel ratios wherein the sensed parameters are formulated from theair-fuel ratios.
 40. The system of claim 39, wherein the controllerincludes means for providing information on a closed-loop status of thecontroller.
 41. The system of claim 40, wherein the pulse width modifierincludes means for varying the pulse width in response to the air-fuelratios and the closed-loop status.
 42. The system of claim 35, whereinthe controller includes means for providing fuel trims in response tothe sensed parameters.
 43. The system of claim 42, wherein the sensorsincludes a universal exhaust gas oxygen UEGO sensor for obtainingair-fuel ratios.
 44. The system of claim 43, wherein the controllerincludes means for providing information on a closed-loop status of thecontroller.
 45. The system of claim 44, wherein the pulse width modifierincludes means for varying the pulse width in response to the air-fuelratios and the closed-loop status.
 46. A vehicle having an internalcombustion engine comprising first and second groups of fuel injectors,the first group of injectors being gasoline injectors, the second groupof injectors being alternative fuel injectors; the vehicle comprising:sensing means for providing information on air for use in the engine,engine temperature, and exhaust gas oxygen content; control means forproviding a fuel control signal having a pulse width in response to theinformation provided by the sensing means; means for selecting a path ofthe fuel control signal; first fuel injection means for controlling thegasoline injection by the gasoline injectors in response to the pulsewidth of the fuel control signal, while the path of the fuel controlsignal is selected to the first fuel injection means; pulse modificationmeans for modifying the pulse width of the fuel control signal when thepath of the fuel control signal is selected to the pulse modificationmeans; and second fuel injection means for controlling the alternativefuel injection by the alternative fuel injectors in response to amodified pulse width of the fuel control signal.
 47. The vehicle ofclaim 46, wherein the pulse modification means includes means forchanging the pulse width of the fuel control signal in response to theinformation provided by the sensing means.
 48. The vehicle of claim 47,wherein the sensing means includes means for sensing values of amanifold air pressure, an engine speed, a coolant temperature, and anintake temperature.
 49. The vehicle of claim 46, further comprisingmeans for providing information on fuel trims.
 50. The vehicle of claim49, wherein: the sensing means includes means for sensing values of amanifold air pressure, an engine speed, a coolant temperature, and anintake temperature; and the pulse modification means including means forchanging the pulse width of the fuel control signal in response to thesensed values and the fuel trim information.
 51. The vehicle of claim49, the pulse modification means further comprises: means for comparingthe sensed values and the fuel trim information to reference values andproviding errors therebetween: and means for changing the pulse width ofthe fuel signal in response to the errors.
 52. The vehicle of claim 46,further comprising means for providing gaseous fuel as the alternativefuel.
 53. The vehicle of claim 52, wherein the alternative fuel is oneof natural gas, propane and hydrogen.
 54. A computer program productcomprising a computer useable medium having computer logic storedtherein for modifying a fuel injection signal having a pulse width, thefuel injection signal being provided by a controller managing a fuelpowered apparatus receiving gasoline and an alternative fuel forelectrical control of a gasoline operated injector and analternative-fuel operated injector, the controller having information ontemperature, exhaust gas oxygen (EGO) content, air-fuel ratio, fueltrims and a control system type, the computer program product including:a mechanism constructed and adapted to obtain the pulse width of thefuel injection signal; a mechanism constructed and adapted to receivethe information on the temperature, EGO content and the fuel trims; amechanism constructed and adapted to modify the pulse width of the fuelinjection signal based on the received information, the modified pulsewidth controlling the alternative fuel supplied by the alternative fuelinjector to the fuel powered apparatus; and a mechanism constructed andadapted to determine whether an error criterion is met based on measuredinformation of the fuel powered apparatus operating on the alternativefuel and desired response information.
 55. The computer program productof claim 54, wherein the mechanism to determine includes: a mechanismconstructed and adapted to obtain a value of the EGO content as themeasured information and to provide a desired EGO content as the desiredresponse information.
 56. The computer program product of claim 54,wherein the mechanism to determine includes: a mechanism constructed andadapted to obtain a value of the air-fuel ratio as the measuredinformation and to provide a desired air-fuel ratio as the desiredresponse information.
 57. The computer program product of claim 54,wherein the mechanism to determine includes: a mechanism constructed andadapted to obtain the fuel trims information as the measured informationand to provide desired fuel trims information as the desired responseinformation.
 58. The computer program product of claim 54, wherein themechanism to modify the pulse width includes: a mechanism constructedand adapted to determine a closed-loop pulse width in response to thepulse width of the fuel injection signal when the control system type isclosed-loop, the closed-loop pulse width, the alternative fuel suppliedby the alternative fuel injector and the determination of the errorcriterion being performed in response to the closed-loop pulse width.59. The computer program product of claim 54, wherein the mechanism todetermine the closed-loop pulse width includes a mechanism constructedand adapted to adjust the closed-loop pulse width based on speed densityinformation of the fuel powered apparatus.
 60. The computer programproduct of claim 54, wherein the mechanism to modify the pulse widthincludes: a mechanism constructed and adapted to determine an open-looppulse width in response to the pulse width of the fuel injection signalwhen the control system type is open-loop, the open-loop pulse width,the alternative fuel supplied by the alternative fuel injector and thedetermination of the error criterion being performed in response to theopen-loop pulse width.
 61. The computer program product of claim 54,wherein the mechanism to determine the open-loop pulse width includes amechanism constructed and adapted to adjust the open-loop pulse widthbased on speed density information of the fuel powered apparatus. 62.Computer-readable media tangibly embodying a program of instructionsexecutable by a computer to perform a method of modifying a fuelinjection signal having a pulse width, the fuel injection signal beingprovided by a controller managing a fuel powered apparatus receivinggasoline and an alternative fuel for electrical control of a gasolineoperated injector and an alternative-fuel operated injector, thecontroller having information on temperature, exhaust gas oxygen (EGO)content, air-fuel ratio and fuel trims, the method comprising: (a)receiving the pulse width of the fuel injection signal; (b) receivingthe information on the temperature, EGO content, and the fuel trims; (c)modifying the pulse width of the fuel injection signal based on thereceived information, the modified pulse width controlling thealternative fuel supplied by the alternative fuel injector to the fuelpowered apparatus; (d) determining whether an error criterion is metbased on measured information of the fuel powered apparatus operating onthe alternative fuel and desired response information; and (e) repeatingthe steps (c) and (d) when the error criterion is not met.
 63. In avehicle controller, in which a fuel injection signal having a pulsewidth is modified, the fuel injection signal being provided by thevehicle controller managing a fuel powered apparatus receiving gasolineand an alternative fuel for electrical control of a gasoline operatedinjector and an alternative-fuel operated injector, the controllerhaving information on temperature, exhaust gas oxygen (EGO) content,air-fuel ratio and fuel trims, a memory medium comprising softwareprogrammed to provide the modified fuel injection signal by a methodcomprising: (a) receiving the pulse width of the fuel injection signal;(b) receiving the information on the temperature, EGO content, and thefuel trims; (c) modifying the pulse width of the fuel injection signalbased on the received information, the modified pulse width controllingthe alternative fuel supplied by the alternative fuel injector to thefuel powered apparatus; (d) determining whether an error criterion ismet based on measured information of the fuel powered apparatusoperating on the alternative fuel and desired response information; and(e) repeating the steps (c) and (d) when the error criterion is not met.